'Practical' and 'Theoretical' Astronomy in Ancient and Late Antique Literature
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http://arxiv.org/abs/1606.01665 - version 2 (footnotes with references added to Sect. 4, 5 and 7) The dichotomy between ‘practical’ and ‘theoretical’ astronomy in ancient and late antique literature Elio Antonello INAF- Astronomical Observatory of Brera Italian Society for Archaeoastronomy [email protected] Abstract. In Plato’s dialogues Republic and Laws, the most important disciplines for the best education of the rulers of the city are identified with arithmetic, geometry and astronomy. Those disciplines, however, are not intended for practical applications, but to reach the truth and see the form of good. In particular, another dialogue, Epinomis, stresses on the relevance of astronomy itself as main discipline, since it coincides with the study of the gods, that is, the planets and the heaven. According to Epinomis, the wise astronomer does not observe the risings and settings of stars for practical applications such as the farmer calendar, but he studies the orbits of the planets. Therefore, the ‘practical’ astronomy of farmers appears intrinsically less important than the ‘theoretical’ astronomy, i.e. the study of the planetary motions. We discuss the possibly far- reaching negative implications of such a specific discrimination. We report some examples taken from Greek and Latin literature illustrating the difficulties of a coherent description of the risings and settings of stars that had been attempted by scholars, and probably had been of little help for farming. We conclude by pointing out the practical importance of astronomy (intended in a broad sense) even today, and of the dangers of the separation or discrimination of disciplines and sub- disciplines for the culture during the present global economic crisis. 1. Introduction Among the ancient philosophers, Plato (428-348 BC) is generally recognized as one of the founders of Western philosophy. In the Dialogues he wrote about logic, ethics, religion, mathematics. In particular he discussed the ideal state or government, and the best education for its rulers. The most important disciplines were arithmetic, geometry and astronomy, since they studied the nature of the numbers and the true motions of the things in the sky, grasped by reason and thought, not by sight. Such a study should have been intended not for a practical application, but to see the truth and the form of good. In the Dialogue Epinomis there is a clear distinction or discrimination between the astronomy of the farmers (i.e. the farming calendar) and the study of planet motions (the planets are gods); we will call the former ‘practical’ astronomy, and the latter ‘theoretical’ astronomy. We will attempt to show the negative implications of that distinction, taking into account some examples taken from ancient and late antique literature. We will mention the problems of astronomical calendars used for farming, and some of their inconsistencies, as they appear in the works of Latin and Greek scholars. Finally, we will point out the dangers of the present distinction or separation of disciplines and sub-disciplines for the culture (e.g. Antonello, 2013b). We remark that the present study is not an essay on the history of philosophy, and it is not a critical discussion of the farming calendars and the related astronomical quandaries; it is just an attempt to point out some problems of the world of culture. 1 2. Plato’s dialogues In the following subsections we will quote at length the Republic, Timaeus and Laws, and then Epinomis. We think it is worth mentioning specific details of those dialogues, since they are of relevance for assessing the issue. 2.1 Republic In the ideal city depicted by Plato, the truly just society needs philosophic rulers, and the education of such philosophers is discussed in book VII of Republic. It begins with the allegory of the cave (corresponding to our visible world), where men live as prisoners, and the shadows they see are taken as the reality. The goal of the education is to free the prisoners from their false opinions and convictions which are based on such ‘reality’. The philosophers have to make the ascent (outside the cave), and see the good, which is beyond the perceived reality (the one inside the cave). Once they have seen the good, they must conclude that it is the cause of all that is correct and beautiful in anything, that it produces both light and its source in the visible realm, and that in the intelligible realm it controls and provides truth and understanding. After that, the philosophers have to come back and live with the prisoners, for the benefit of the community. Education isn’t putting knowledge into souls that lack it, like putting sight into blind eyes (Republic, VII, 518b, c). The power to learn is present in everyone’s soul, and education takes for granted that ‘sight’ is there, but it isn’t turned the right way, so the education tries to redirect it appropriately (Republic, VII, 518d). What are the disciplines, apart from the dialectics, that draw the soul from the realm of becoming to the realm of what is? They have to do with the number, and not just in the practical way that is useful for a warrior ruler, but in such a way that a philosopher-ruler learns to rise up out of becoming and grasp being. The disciplines are therefore computation and arithmetic, plane and solid geometry, and finally astronomy. Astronomy should not consist in a better awareness of the seasons, months, and years, which is no less appropriate for a general than for a farmer or a navigator (Republic, VII, 527d). It is not true that astronomy by itself compels the soul to look upward and leads it from things here to things there. According to Plato, indeed, astronomy as practiced by scholars makes the soul look very much downward; it is useful for practical applications, but a philosopher shall not be afraid to propose things that apparently are of no utility to most people. Plato cannot conceive of any subject making the soul looking upward except one concerned with that which is, and that which is invisible; the truth consists just in that invisible thing (Republic, VII, 529b). 2.2 Timaeus In the Timaeus, Plato presents an account of the formation of the universe. The god created firstly its soul, and then he made a moving image of eternity according to number. Time came to be after the model of that which is eternal. The good craftsman brought into being the Sun, the Moon and five other stars, for the begetting of time. He made the fixed stars and spread these gods throughout the whole heaven. Then there were two other generations of gods, “who are called by names we know”, beginning with Earth and Heaven (Timaeus, 41a). Their task was to make the mortal creatures, weaving what is mortal to the immortal seed (the soul) sowed by the craftsman. The eyes were the first of the organs of the head to be fashioned by them (Timaeus, 45b). Our sight has proved to be a source of supreme benefit to us, in that none of our statements about the universe could ever have been made if we had never seen the heaven. Our ability to see the periods of day and night, of months and of years, of equinoxes and solstices, has led to the invention of number, and has given us the idea of time and opened the path to inquiry into the nature of the universe. These pursuits have given us philosophy, a gift from the gods to the mortal race whose value neither has been nor ever will be surpassed. The god “invented sight and gave it to us so that we might observe the orbits of intelligence in the universe and apply them to the revolutions of our own understanding. For there is a kinship between them, even though our revolutions are disturbed, whereas the universal orbits are undisturbed” (Timaeus, 47a - c). 2 2.3 Laws In the Laws, the old philosopher discusses the codes of law of a new city, and the book VII deals with the education. Three disciplines are mentioned, computation and study of numbers, measurements of lines, surfaces and solids, and the mutual relationship of the heavenly bodies as they revolve in their courses. These subjects must be studied in minute detail not by the general public, but only by a chosen few, even though those disciplines would be actually important for all (Laws, VII, 817e-818a). Plato affirms that he is not just deterred by the way people commonly neglect that subject, but he is even more appalled at those who have actually undertaken those studies, but in the wrong manner. Indeed, total ignorance over an entire field is never disastrous; much more damage is done when a subject is known in detail, but has been improperly taught (Laws, VII, 819a). Plato appears particularly amazed at the general ignorance about commensurables and incommensurables, blushing not only for himself but also for the Greeks in general (Laws, VII, 819d-820b). There is, moreover, another intolerable thing concerning astronomy: people generally believe that the heavenly bodies never follow the same path; this is the reason for the name ‘planets’, i.e. wanderers. According to Plato, that is blasphemy: actually the great gods (Sun, Moon, planets) perpetually describe just one fixed orbit, although it is true that to all the appearances its path is always changing (Laws, VII, 821a-822a). The book XII of the Laws describes the Nocturnal Council, its members (such as the ten Guardians of Laws), and their duties; the Council has to meet daily from dawn, to muse on legislation.